Leaves have yellowed

The problems listed below assume that pests are not present on the plant in question. If you suspect that pests may be responsible for your problems, please refer to the Pest Page for more details.

Symptom/Detail Link/Cause Description/Solution
Leaf spots were yellowed and then became brown or black and dry. Sunburn
When leaves are exposed to direct sunshine for even short periods, they can overheat and become sunburned. Never allow direct sunlight to hit any leaf surface during the bright part of the day (11 am to 3 pm). You can use sheer curtains or frosted glass to diffuse the light. You can only prevent more leaves from becoming damaged, but those that are already damaged will not recover and you will have to wait for them to be shed normally.
Older leaves yellowed and then became brown or black and dropped off. Normal Older leaves are shed by orchids normally. They first begin to yellow before dying off completely. This cycle is perfectly normal and does not indicate any sort of a problem. The life span of an orchid leaf is usually 3 to 5 years. For deciduous types, the life span is one year.
Younger leaves yellowed and then became brown or black and dropped off. Temperature shock. Younger leaves should never yellow and drop off. Usually a cold shock through water temperature or draughts can be the cause. Ensure that water temperature is warm before using it on your plants and that there are no draughts hitting the plant through poor window seals or open doorways nearby. Air conditioning hitting plants directly can also lead to this problem.
Younger leaves became mushy or translucent, and then turned black. Crown rot
Typically this happens on plants where the young leaves form a cup, such as in phalaenopsis. Any water accumulating in this area will usually lead to this problem. Try to carefully remove the affected areas and treat with fungicide to prevent the area from spreading. Growth will not resume from this point, so you will have to wait for a side growth or keiki to develop. In future, ensure your plants are completely dry by evening. Avoid misting plants directly, and only mist around the plant to increase humidity in future.
Younger leaves yellowed (spots or mottling) and then developed abnormally. Mineral deficiency
Younger leaves should never yellow. Ensure that your fertilizer is properly balanced for orchids, and contains micro-nutrients or trace elements. A shortage of these will cause leaves to discolor and develop abnormally. Correcting this problem will not fix the leaves that are already damaged. They will need to be replaced in the normal cycle of growth.
Younger leaves started normally but then yellowed as they matured. Mineral toxicity
This is usually more prevalent in true epiphytic paphiopedilums (lady-slippers) such as lowii and parishii, and their hybrids. Being true epiphytes, these species have a low tolerance for phosphorous. Check the fertilizer you're using for the levels of phosphorous it contains (this is the middle number in the formula). If the level of phosphorous is high relative to the other two numbers, then switch to a fertilizer with less phosphorous. The problem will not correct itself on older leaves, but the new ones should now develop properly.
Mature leaves yellowed and turned black Cultural
If little puddles of water sit on leaves for long periods of time, then the leaf will usually turn yellow, then brown and finally black. This is because the leaf cells in that area have died. Always ensure that your plants are completely dry before nightfall. Be especially careful of small depressions in leaf surfaces that can trap water.
Start over Click Here I didn't find my answer, so I want to start over again.
You can also use the browser "<- Back" button to navigate through the diagnosis.